1. Field of the Invention
The present invention relates to a method of indicating desirability of a shift operation to be performed on a manual gearbox, and more particularly to a method which senses a state of the vehicle operation (including the engine operation) requiring a shift operation of the manual gearbox and indicates the necessity of the shift operation of the manual gearbox.
2. Description of Background Information
By suitably selecting the gear position of a manual gearbox of a vehicle in accordance with a parameter of the vehicle operation such as the load applied to the vehicle, the fuel consumption in a preselected running mode of the vehicle, as well as in the actual running condition after the vehicle has been brought into service, can be improved. Conventionally, various methods for indicating a desirable gear position have been proposed. For example, Japanese Patent Application Laid Open Number 55-31671 discloses a method in which the rotational speed of the engine and the throttle position are monitored, and gearbox operation requiring an up-shift operation or a down-shift operation is indicated according to the monitored rotational speed of the engine and the throttle position.
Japanese Utility Model Publication No. 55-34283 discloses a method in which an integration value of the distance covered by the vehicle (mileage) or the running time of the engine is detected in order to compensate for a time-induced change of the indication operation.
On the other hand, it is known that the driveability of a new car is not as good as the driveability of a car which has passed a breaking-in period, because of frictional losses of the engine and power transmission system. Further, it has been experienced that the running-in period can be completed sooner as the frequency of a high speed drive of the engine increases, even though the same distance is covered by the vehicle.
Therefore, if a reference value used to indicate a shift operation of a manual gearbox, such as a reference speed level, is determined for a new car before the breaking-in period to be the same as the level for a car which has already passed the breaking-in period, it would cause the use of an undesirably low speed range of engine rotation. Thus, the driveability of the vehicle would be deteriorated in such a case.
In addition, it is conceivable to raise the reference vehicle speed of an up-shift operation as the engine temperature decreases. However, when the temperature of the engine is very low, raising of the reference vehicle speed depending on a total running time of the vehicle would rather cause an adverse effect on the driveability of the vehicle.